A process for the hydroformylation of olefins

ABSTRACT

An Oxo process wherein an olefin is reacted with hydrogen and carbon monoxide in the presence of a cobalt carbonyl and a trioxadiphosphabicyclooctane, preferably in the presence of a trialkyl amine.

United States Patent [191 Definer et a1.

[ 51 Apr. 3, 19,73

[54] A PROCESS FOR THE HYDROFORMYLATION OF OLEFINS [75] Inventors: John F. Definer, Glenshaw; Edmond R. Tucci, Pittsburgh; Helen I. Thayer, John V. Ward, both of Oakmont, all of Pa.

[73] Assignee: Gulf Research and Development Company, Pittsburgh, Pa.

[22] Filed: Aug. 23, 1966 [21] Appl. No.2 574,305

[52] US. Cl. ..260/604 HF, 260/598, 260/632 HF, 260/439, 252/431, 260/617 HF [51] Int. Cl ..C07c 45/08 [58] Field of Search..260/927, 439, 604 HF, 632 HF, 260/598; 252/431 [56] References Cited UNITED STATES PATENTS 2,966,427 12/1960 Breining ..117/106 D 3,130,237 4/ 1964 Wald ..260/638 3,278,612 10/1966 Greene ..260/604 X 3,239,569 3/1966 Slangh et a1. ..260/604 X 3,102,899 9/1963 Cannell ..260/439 57 ABSTRACT An 0x0 process wherein an olefin is reacted with hydrogen and carbon monoxide in the presence of a cobalt carbonyl and a trioxadiphosphabicyclooctane, preferably in the presence of a trialkyl amine.

8 Claims, No Drawings cobalt carbonate, can also'be used. Most of these salts are soluble in most of the olefinic feeds supplied to the hydroformylation reaction zone, but when they are not, they can be supplied in an inert, liquid hydrocarbon in which they are soluble, such as benzene, xylene, naphtha, heptane, decane, etc. Although the catalyst is supplied in the form of a cobalt salt to the hydrofor-- mylation reaction zone, under the conditions existing therein the salt reacts with carbon monoxide, preferably in the presence of hydrogen, to form a cobalt carbonyl, that is, one or more of the following: cobalt hydrocarbonyl, HCo(CO) dicobalt octacarbonyl, Co (CO) and/or tetracobalt dodecacarbonyl, Co (CO), As defined herein cobalt carbonyl will refer to any one or all of the specific cobalt carbonyls referred to above. It is generally believed that the cobalt carbonyl is the active form of catalyst for the hydroformylation reaction.

Since cobalt carbonyls are thermally unstable and will easily decompose to elemental cobalt and carbon monoxide, it is necessary to maintain a high pressure of hydrogen and carbon monoxide in the hydroformylation reaction zone to inhibit such decomposition at the elevated temperatures existing in the hydroformylation reaction zone. At the end of the reaction period, the reaction product will consist largely of an aldehyde havingone carbon more than the olefinic charge, plus unreacted hydrogen and carbon monoxide and some alcohol, corresponding to the aldehyde, carrying dissolved cobalt carbonyl. The unreacted hydrogen and carbon monoxide can rather easily be separated from the reaction product, for example, by flash distillation, but the cobalt carbonyl is removed only with difficulty. It is obvious that if the aldehyde product, as such, is desired, it'would be necessary to remove cobalt car bonyl therefrom. In most cases the aldehyde is subjected to hydrogenation conditions in the presence of a hydrogenation catalyst, such as nickel, to convert the aldehyde to the corresponding 'alcohol. in such case it becomes even more imperative to remove cobalt carbonyl from the aldehyde being hydrogenated, since at the lower pressures employed in the hydrogenation reactor cobalt carbonyl will decompose to cobalt and carbon monoxide, the latter being undesirable in the hydrogenation reaction zone, since it has a tendency to poison the hydrogenation catalyst, such as nickel, which is generally used.

It has been customary, therefore, to subject the hydroformylation reaction product to a decobalting operation to remove cobalt carbonyl therefrom. This has generally involved subjecting the hydroformylation reaction product to temperature and pressure conditions favoring the decomposition of cobalt carbonyl to elemental cobalt. and carbon monoxide. Elemental cobalt is difficult to remove from the hydroformylation reaction product, and it has a tendency to plug the lines leading to and from the decobalter and for some to find its way into the hydrogenation reactor. The removal of such cobalt adds significantly to the overall cost of the hydroformylation reaction. Cobalt so obtained, in addition, has to be discarded or, by a tedious procedure may, perhaps, be converted back to the original cobalt salt or cobalt carbonyl for use in the hydroformylation reaction zone. y

We have found, however, that the abovedifficulties can be avoided by employing in the hydroformylation reaction zone a cobaltcatalyst such as defined above and a specific trioxadiphosphabicyclooctane selected from the group of 3,5,8-tri(alkyl)-2,6,7-trioxa-l ,4- diphospha-bicyclo[2.2.2] octane, 3,5,8-tri(aryl)-2,6,7- trioxa-l,4-diphospha-bicyclo [2.2.2]octane, and 3,5,8- trihydro-2,6,7trioxa-1,4-diphosphabicyclo[2.2.2]octane'having the following structural formula:

wherein R R and R the same or different, are straight chain or branched alkyl substituents having from 1 to 16 carbon atoms, preferably 1 to 10 carbon atoms, or aryl substituents having from 6 to 16 carbon atoms, preferably from 6 to 10 carbon atoms, or hydrogen. Specific examples of alkyl substituents are methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, nheptyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, isopropyl, 2-methylbutyl, 2-ethylpentyl, 3-butylhexyl, 4-pentyldecyl, 2,2'-dimethyldecyl, 3-methyl- 4-ethyldecyl, S-propylhexyl, 3-methyldodecyl, 6-ethyldodecyl, 3,3-dimethyltetradecyl, 2-butylhexadecyl, etc., and of aryl substituents are phenyl, tolyl, xylyl, 1,3,5-trimethylphenyl, ethylphenyl, propylphenyl, butylphenyl, hexylphenyl, decylphenyl, dodecylphenyl, tetradecylphenyl, hexadecylphenyl, etc. Specific examples of such compounds that can be employed herein include 3 ,5 ,8-trihydro-2,6,7-trioxa-l ,4-diphosphabicyclo[2.2.2]3,5,8 trimethyl-2,6,7-tri0xa-l ,4- diphospha-bicyclo[2.2.2]octane, '3,5,8-tri(n-butyl)- 2,6,7-trioxa-1,4-diphospha-bicyclo[2.2.2]octane,

3,5 ,8-tri(n-heptyl)-2,6,7-trioxal ,4 diphosphabicyclo[2.2.2]octane, 3,5,8-tri(n-dodecyl)-2,6,7-trioxa-l ,4-diphospha-bicyclo[ 2.2.2 ]octane, 3 ,5 ,8-tri(n-hexadecyl )-2,6,7-trioxa-l ,4-diphospha-bicyclo[2.2.2 ]octane, 3 ,5-dimethyl-8-hydro-2,6,7-trioxa-l ,4- diphospha-bycyclo[2.2.2]octane, 3,5-di(n-hexyl)-8- hydro-2,6,7-trioxal ,4-diphospha-bicyclo[2.2.2100- tane, 3 ,5-diethyl-8-hydro-2,6,7-trioxa-l ,4-diphosphabicyclo[2.2.2]octane, 3-n-octyl-5,8-dihydro-2,6,7-

trioxa-l ,4-diphospha-bicyclo 2.2.2]octane, 3-ndodecyl-dodecyl-S,8-dimethyl-2,6,7-trioxa-l ,4- diphospha-bicyclo[2.2.2]octane, 3-hydro-5,8-

di( isopropyl )-2 ,6,7-trioxal ,4-diphospha-bicyclo[ 2.2.2 ]octane, 5-n-butyl-3,8-di(n-nonyl)-2,6,7-trioxa-l ,4- diphospha-bicyclo 2.2.2 ]octane, 3 ,5 ,8-triphenyl-2 ,6 ,7- trioxal ,4-diphospha-bicyclo[2.2.2]octane, 3,5 ,8- tritolyl-2,6,7-trioxa- 1 ,4-diphospha-bicyclo[ 2.2.2]octane, 3,S-diphenyl-8-hydro-2,6,7-trioxal ,4-diphosphabicyclo[ 2.2.2 octane, 3 ,5-dicumyl-8-hydro-2 ,6,7-trioxhydroformylation al ,4-diphospha-bicyclo[2.2.2 loctane, 3-methyl-5-nbutyl-8-phenyl-2,6,7-trioxa-1 ,4-diphospha-bicyclo[ 2.2.2loctane, 3-hydro-5-n-octyl-8-tolyl-2,6,7-trioxal ,4-diphospha-bicyclo 2.2.2 octane, 3 ,5-dihydro 8- butylphenyl-2,6,7-trioxal ,4-diphospha-bicyclo[2.2.2 ]octane, 3 ,5-dihydro-8-xylyl-2,6,7-trioxa-1,4- diphospha-bicyclo[2.2.21octane, 3,5-dimethyl-8-(6- ethyldodecyl)-2,6,7-trioxa-1,4-diphospha-bicyclo[ 2.2.2 ]octane, 3 ,8-diphenyl--hydro-2,6,7-trioxa-1,4- diphospha-bicyclo 2 .2 .2 octane 3 ,8-ditolyl-5-hydro- 2,6,7-trioxa-l,4-diphospha-bicyclo[2.2.2]octane, 5,8- diphenyl-3-hydro-2,6,7-trioxa-1 ,4-diphosphabicyclo[2.2.2]octane, 5,8-diphenyl-3-isopropyl-2,6,7- trioxa-l,4-diphospha-bicyclo[2.2.2]octane, etc. For purposes of simplicity herein, we shall refer throughout the specification, except in specified examples, to these compounds as TDB. In the specific examples TDB will refer to the specific compound 3,5,8-trihydro-2,6,7- trioxa-l ,4-diphospha-bicyclo[2.2.2]octane. We believe that under the hydroformylation reaction conditions,

- the TDB, as a ligand, combines with the cobalt carbonyl and forms a complex therewith. By ligand we intend to include TDBs which contain an element with an electron pair that can form a coordination compound with a metal compound.

Although the complex defined above is thermally stable and can be used, as such, in a number of reactions without appreciable decomposition thereof, the complex can be rendered even more thermally stable be employing in admixture therewith a selected amount of a trialkyl amine having a pK acidity of at least about +8 but no greater than about +15, preferably a pK, acidity of about +10 to about +13. By pK, acidity we mean to refer to the negative logarithm of the Bronsted acid dissociation constant. Weak bases have low pK, values, while strong bases have high pK, values. Although there may be some tendency for the trialkyl amine to complex with the cobalt carbonyl, we are of the opinion that only a small amount of such complexing takes place, since there is a greater tendency for a complex to form between cobalt carbonyl and the TDB, as set forth above.

By trialkyl amine" that we employ herein for increased catalyst thermal stability, we intend to include those trialkyl amines whose individual alkyl substituents will have from 1 to 16 carbon atoms, preferably from one to about 12 carbon atoms, as well as those whose alkyl substituents carry one or more a1- dehydic, alcoholic, chlorine, fluorine or phenyl substituents thereon. Each of the individual alky l substituents attached to the nitrogen atom of the amine, moreover, does not have to be similar to another substituent on the same amine. Specific amines that can be employed herein include trimethylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-dodecylamine, tri-nhexadecylamine, tribenzylamine, N,N-dimethylbenzylamine, N,N-dimethylnapthylamine, N,N-methylbutylbenzylamine, N-N-butylethylbenzylamine, N,N- diethyldodecylamine, 2,2,2"-iminotriethanol, 2,2',2"- iminotriethylchloride, 4,4',4"-iminotributylchloride, l,l,1"4,4',4"-iminotributyraldehyde, 7,7,7"-imino-trihcptaldehyde, etc.

easily obtained and employed herein. In a preferred embodiment it is obtained in situ in the hydroformylation reaction zone. Thus, one of the cobalt salts, for example, one of those defined above is introduced into the hydroformylation reaction zone along with one of the defined TDBs, the olefin to be subjected to hydroformylation reaction, hydrogen and carbon monoxide. Any olefinic compound that can be subjected to hydroformylation reaction and can be converted therein to aldehyde having one more carbon than said olefin can be employed. Representative examples of olefins that can be employed include propylene, butene-l, pentene-l, hexene-l, heptene-l, octene-l decene-l, tetradecene-l, hexadecene- 1 pentene-2, hexene-2, heptene-Z, octene2, 4-methy1-lpentene, 2,4,4-trimethy1-1-pentene, 4-methy1-2-pentene, 2,6-dimethyl-3-heptene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, 4-methyl-1cyclo-hexene, etc. The molar ratio of hydrogen to carbon monoxide can be from about 5:1 to about 0.521, preferably from about 1:1 to about 2: 1. The amount of hydrogen and carbon monoxide needed is at least that amount stoichiometrically required for addition to the olefinic compound, although from about 1% to about 3 times the amount stoichiometrically required can be employed. The amount of TDB employed is from about 0.5 to about 10, preferably from about 2 to about 6 mols per mol of cobalt carbonyl. When an amine is employed it is also introduced into the reaction zone. From about 0.5 to about 10, preferably from about 2 to about 4 mols of amine per mol of cobalt carbonyl can be employed.

The reaction conditions in the hydroformylation reaction zone can vary over a wide range. Thus the temperature can be from about 200 to about 475 F preferably from about 275 to about 325 F., while the pressure can be from about 500 to about 5,000 pounds per square inch gauge, preferably from about 1,000 to about 3,000 pounds per square inch gauge. Reaction time can be from about 5 minutes to about 5 hours, but preferably will be from about 30 minutes to 120 minutes.

As a result of the above the cobalt salt will be con- I verted to cobalt carbonyl and the latter, in turn, will complex with the TDB to form the new complex defined above, which becomes the hydroformylation reaction catalyst. At the end of the reaction period the converted product obtained will contain from about 15 to about per cent by weight of aldehyde having one more carbon than said olefinic charge and from about 10 to about 50 per cent by weight of alcohol corresponding to said aldehyde. Also present with the converted product, of course, are unreacted hydrogen and carbon monoxide but also the cobalt carbonyl-TDB complex and the trialkyl amine, when the latter is also employed. The unreacted hydrogen and carbon monoxide can be recovered from the reaction product in any convenient manner, for example, by flashing at a temperature of about 25 to about C. and a pressure of about 15 to about 500 pounds per square inch gauge. The aldehyde and alcohol present in the resulting reaction product can be removed therefrom in any convenient manner, for example, by subjecting the resulting reaction mixture to a temperature of about -30 to about 200 C. and a pressure of about 0.001 to about 760 millimeters absolute pressure. As a result of such action the aldehyde and alcohol are flashed off together or separately and left behind is the cobalt catalyst complex, trialkyl amine and/or solvent, when used and a small amount of polymerization product, which can be primarily acetals, hemiacetals and esters. A feature of the present process is that less polymer is formed herein than is generally formed during the conventional hydroformylation reaction process wherein uncomplexed cobalt carbonyl is employed as catalyst. Another additional, and quite important feature of the present process, is that the ratio of normal aldehyde and/or normal alcohol to iso aldehyde and/or iso alecho] is high, from about 4:1 to about 7:1. Thus, normal aldehydes can be aldolized to yield 2-ethylhexanol which is useful as a plasticizer, or they can be hydrogenated to normal alcohols which are useful as commercial solvents or plasticizers. The cobalt carbonyl complex herein, along with the trialkyl amine, when used, can be recovered from the polymer in any convenient manner, for example, by ion exchange, solvent extraction or distillation, or can be permitted to remain in combination with the polymer, which can serve as solvent therefor, and can be reused during the hydroformylation reaction as previously defined. This procedure can be repeated many times, since the cobalt carbonyl complex defined herein is stable and will not decompose under the reaction and recovery conditions employed herein.

The cobalt carbonyl complex catalyst need not be formed in situ, as defined above, but can be preformed. Thus a mixture of cobalt carbonyl, such as defined 1 above, can be combined with one of the TDBs,

- ture along with the TDB or it can be added to the complex in the hydroformylation reaction zone. If desired, the cobalt carbonyl complex can be obtained. as defined immediately above by substituting one of the previously defined cobalt salts for the cobalt carbonyl.

In such case, however, at least about one to about mols of carbon monoxide, preferably about one to about 8 mols of carbon monoxide, relative to the cobalt salt must also be present. The resulting mixture can be used as such in the hydroformylation reaction zone as catalyst, or if desired the cobalt carbonyl complex can be recovered from the mixture in any suitable manner, for example, by ion exchange, solvent extraction or distillation.

The process of this invention can further be illustrated by the following:

Into a 500 milliliter stainless steel autoclave there was placed 100 milliliters of benzene and l 1 grams of a solution containing 8 milliliters of benzene and 4 milliliters of the cobalt salt of 2-ethylhexanoic acid. The autoclave was flushed with nitrogen gas and then pressured with synthesis gas containing 1.2 mols of hydrogen per mol of carbon monoxide to a pressure of 300 pounds per square inch gauge. The autoclave was depressured to atmospheric pressure and repressured with synthesis gas several times. The autoclave was finally pressured with synthesis gas to about 2,300 pounds per square inch gauge at room temperature and then heated to 350 F. within to minutes. A temperature of 350 F. and a pressure of 3500 pounds were maintained for 1 hour. The autoclave was cooled to F. and thereafter slowly depressured to atmospheric pressure.

To the 2.0 grams of dicobalt octacarbonyl thus formed in the autoclave there was added 1.2 grams of 3 ,5 ,8-trihydro-2,6,7-trioxa-1 ,4-diphospha- 'bicyclo[2.2.2]octane, 3.9 grams tributyl amine, 8.0

grams of propylene, and 650 pounds per square inch gauge of hydrogen and carbon monoxide in a molar ratio of 1.221. The reaction mixture was heated to 310 F. for 1 hour, and maintained at 1,000 pounds per square inch gauge with synthesis gas to obtain a reaction product containing substantial amounts of aldehyde, or the corresponding alcohol, having one more carbon than the reactant olefin. At the end of the reaction period the autoclave was cooled to about 75 F. and then depressured to atmospheric pressure and the product analyzed for its composition. The results obtained indicated a selectivity to normal butyraldehydes or butanols of 82 per cent and a conversion of about 70 per cent. The product distribution indicated 65 weight per cent butyraldehydes and 35 weight per cent butanols.

Obviously many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a process wherein an olefin is subjected to hydroformylation with hydrogen and carbon monoxide at elevated temperatures of about 200 to about 475 F. and elevated pressures of about 500 to about 5,000 pounds per square inch gauge to obtain a product containing predominantly an aldehyde having one more carbon than said olefin, the improvement which comprises carrying out the reaction in the presence of a cobalt carbonyl. and a trioxadiphospha-bicyclooctane selected from the group consisting of 3,5,8-tri(alkyl)- 2,6,7-trioxa-l ,4-diphospha-bicyclo[ 2.2.2 ]octane, 3,5,8tri(aryl)-2,6,7-trioxa- 1 ,4-diphosphabicyclo[2.2.2]octane, and 3,5,8-tri-hydro-2,6,7-trioxal ,4-diphosphabicyclo[ 2.2.2]octane.

2. The process of claim 1 wherein said trioxadiphosphabicyclooctane is 3,5,8-tri(alkyl)2,6,7- trioxal ,4-diphospha-bicyclo[2.2.2 ]octane.

3. The process of claim 1 wherein said trioxadiphosphabicyclooctane is 3,5,8-tri(aryl)-2,6,7-trioxal ,4-diphospha-bicyclo[2.2.2]octane.

4. .The process of claim 1 wherein said trioxadiphosphabicyclooctane is 3,5,8-trihydro-2,6,7-trioxal ,4-diphospha-bicyclo 2 .22 ]octane.

5. The process of claim 1 wherein the reaction is carried out in the additional presence of tri-n-butyl amine.

6. The process of claim 1 wherein the olefin is propylene.

7. The process of claim 1 wherein said catalyst is recovered and reused in a subsequent hydroformylation reaction.

8. The process of claim 1 wherein the cobalt carbonyl is dicobalt octacarbonyl.

i I! I! 

2. The process of claim 1 wherein said trioxadiphosphabicyclooctane is 3,5,8-tri(alkyl)-2,6,7-trioxa1,4-diphospha-bicyclo(2.2.2)octane.
 3. The process of claim 1 wherein said trioxadi-phosphabicyclooctane is 3,5,8-tri(aryl)-2,6,7-trioxa-1,4-diphospha-bicyclo(2.2.2)octane.
 4. The process of claim 1 wherein said trioxadiphosphabicyclooctane is 3,5,8-trihydro-2,6,7-trioxa-1,4-diphospha-bicyclo(2.2.2)octane.
 5. The process of claim 1 wherein the reaction is carried out in the additional presence of tri-n-butyl amine.
 6. The process of claim 1 wherein the olefin is propylene.
 7. The process of claim 1 wherein said catalyst is recovered and reused in a subsequent hydroformylation reaction.
 8. The process of claim 1 wherein the cobalt carbonyl is dicobalt octacarbonyl. 